1. Field of the Invention
The present invention relates to a high-output electric motor which is small and lightweight, and is suitably employed as a servomotor for a robot, a machine tool, an office automation apparatus and the like.
2. Prior Art
One conventional electric motor includes a cylindrical rotor rotatably received in and supported on a housing and a stator disposed in and fixedly secured to the housing to encompass the rotor. For obtaining a high-output electric motor of such construction, it is necessary to increase the outer diameter of the rotor or to lengthen the rotor axially thereof, so as to increase the surface area of the rotor. In that case, however, the weight and moment of inertia of the rotor are increased unduly, so that the motor becomes unsuitable for driving a small apparatus.
To overcome the above problems, a motor which is lightweight and has low moment of inertia and high torque has been proposed, for example, in Japanese patent application Laid-Open No. 60-66658. The motor includes rotor disks each having a plurality of permanent magnets disposed in a radial manner and stator rings each having a winding or coil, the rotor disk and the stator ring being disposed alternately in an axial direction so that the magnets of each rotor disk face the coil of each stator disk. The aforementioned motor, however, has a drawback that the heat generated in the inner peripheral portion of each stator disk is not sufficiently dissipated.